This invention relates to a portable telephone.
In a microcellular portable telephone system such as the PHS (Personal Handyphone System) which is one of radio communication standards of Japan, a large overall calling area can be structured by arranging a plurality of small calling areas (cells). In the United States of America, PCS (Personal Communication System) has been used as the similar system.
More specifically, as for instance in FIG. 6, a calling area also referred to as a radio zone Z11, is comprised of a base station CS11, and the radio zones Z12 through Z1N are respectively comprised of the base stations CS12 to CSlN. In this case, the radius of zones Z12 through Z1N varies according to factors such as the surrounding conditions. However, this radius is generally, for example, about 100 meters and a maximum of about 400 meters.
The radio zones Z11 through Z1N are fundamentally established in proximity to each other and these zones Z11 through Z1N comprise the calling area also referred to as a position registration area A1.
Further, the radio zones Z21 through Z2M are comprised of the base stations CS21 through CS2M, and the position registration area A2 is comprised of these zones Z21 through Z2M. Hereafter a plurality of position registration areas (not shown in the drawing) are comprised in the same way. In this case, the position registration areas are generally located in proximity to each other to comprise a larger calling area overall. Though not shown in the drawing, the base stations CS11 through CS1N, CS21 through CS2N, and so on are linked to city telephone switching equipment and the data base station (PHS control station).
As shown for instance in the position 1 of FIG. 6, when the PHS terminal 1 is within the zone Z11 and the power is turned on, the terminal 1 sends a position registration request to the base station CS11, and the data base station registers the information that the terminal 1 is in the zone Z11. The terminal 1 is also notified from the base station CS11 with an identifier code CS-ID of the base station CS11.
However, as shown in the position 2 of FIG. 6, with power on at the terminal 1, when the terminal 1 moves from the zone Z11 to zone Z12, an adjacent zone in the same position registration area A1, the terminal 1 is this time notified from the base station CS12 with an identifier code CS-ID of the base station CS12.
Further, as shown in the position 3 of FIG. 6, with power on at the terminal 1, if the terminal 1 moves from zone Z11 to Z21 and into another position registration area A2, this time the terminal 1 makes a position registration request to base station CS21. The information that the terminal 1 is in the zone Z21 is registered in the data base station. The base station CS21 sends an identifier code CS-ID to the terminal 1 from the base station CS21.
In this way, even if the position of the terminal 1 changes, its position can be monitored by the data base stations by means of the individual position registration areas. The terminal 1 is of course, able to therefore send out messages and also to receive messages.
FIG. 5 shows the format for the identifier code CS-ID sent from a base station to the terminal 1. The first nine bits of the identifier code CS-ID indicate the identifier code of the business using PHS, and the following 33 bits indicate the outdoor public telephone extension identifier code for specifying the base station.
This outdoor public telephone extension identifier is comprised of a total call-up area number for specifying the position registration areas A1, A2 and so on, and an extension identifier code for specifying the radio zone according to the position registration area.
The terminal 1 therefore knows the individual base station to which it is to be or has been connected.